| 摘要 |
PROBLEM TO BE SOLVED: To provide a projecting optical system, both sides of which are telecentric and which is made to be satisfactorily achromatic for a plurality of wavelength bands from a visible area to a near-ultraviolet area, while high image forming performance is ensured. SOLUTION: The projecting optical system includes: a first lens group 1 of positive power, which includes a first lens disposed on a highest magnifying side; a second lens group, which is the lens group of negative power and is composed of lenses from the first negative lens that satisfies ¾Hn/Y¾<0.75 to the first lens that satisfies Ln/L1a>0.15 among subsequent lenses including the negative lens; and a third lens group, which is the lens group of positive power and is composed of remaining lenses including a diaphragm. In this case, the third lens group includes at least two positive lenses that satisfy 0.662<0.00055×νh+P, and the projecting optical system satisfies 1<¾f12/f3¾<5, wherein f12 is the combined focal distance (mm) of the first and second lens groups, and f3 is the focal distance (mm) of the third lens group. COPYRIGHT: (C)2011,JPO&INPIT |
